factorising both progress trackers into struct progressTracker.

service/service.go

@@ -31,24 +31,6 @@ type Error struct {
 	Message string `json:"message"`
 }
 
-type progressTrackingReader struct {
-	io.Reader
-	Oid       string
-	TotalSize int64
-	Writer    *bufio.Writer
-	ErrWriter *bufio.Writer
-	bytesRead int64
-}
-
-func (r *progressTrackingReader) Read(p []byte) (n int, err error) {
-	n, err = r.Reader.Read(p)
-	if n > 0 {
-		r.bytesRead += int64(n)
-		api.SendProgress(r.Oid, r.bytesRead, n, r.Writer, r.ErrWriter)
-	}
-	return
-}
-
 type writerAtWrapper struct {
 	w io.Writer
 }
@@ -57,27 +39,32 @@ func (waw *writerAtWrapper) WriteAt(p []byte, off int64) (n int, err error) {
 	return waw.w.Write(p)
 }
 
-type progressTrackingWriter struct {
-	writer         io.WriterAt
-	oid            string
-	totalSize      int64
-	writerResponse *bufio.Writer
-	errWriter      *bufio.Writer
-	bytesWritten   int64
+type progressTracker struct {
+    Reader      io.Reader
+    Writer      io.WriterAt
+    Oid         string
+    TotalSize   int64
+    RespWriter  *bufio.Writer
+    ErrWriter   *bufio.Writer
+    bytesProcessed int64
 }
 
-func (ptw *progressTrackingWriter) WriteAt(p []byte, off int64) (int, error) {
-	n, err := ptw.writer.WriteAt(p, off)
-	if err != nil {
-		return n, err
+func (rw *progressTracker) Read(p []byte) (n int, err error) {
+	n, err = rw.Reader.Read(p)
+	if n > 0 {
+		rw.bytesProcessed += int64(n)
+		api.SendProgress(rw.Oid, rw.bytesProcessed, n, rw.RespWriter, rw.ErrWriter)
 	}
+	return
+}
 
+func (rw *progressTracker) WriteAt(p []byte, off int64) (n int, err error) {
+	n, err = rw.Writer.WriteAt(p, off)
 	if n > 0 {
-		ptw.bytesWritten += int64(n)
-		api.SendProgress(ptw.oid, ptw.bytesWritten, n, ptw.writerResponse, ptw.errWriter)
+		rw.bytesProcessed += int64(n)
+		api.SendProgress(rw.Oid, rw.bytesProcessed, n, rw.RespWriter, rw.ErrWriter)
 	}
-
-	return n, nil
+	return
 }
 
 func Serve(stdin io.Reader, stdout, stderr io.Writer) {
@@ -148,21 +135,20 @@ func retrieve(oid string, size int64, action *api.Action, writer, errWriter *buf
 	}()
 
 	waw := &writerAtWrapper{file}
-
-	ptw := &progressTrackingWriter{
-		writer:         waw,
-		oid:            oid,
-		totalSize:      size,
-		writerResponse: writer,
-		errWriter:      errWriter,
+	progressWriter := &progressTracker{
+		Writer:         waw,
+		Oid:            oid,
+		TotalSize:      size,
+		RespWriter:     writer,
+		ErrWriter:      errWriter,
 	}
 
 	downloader := manager.NewDownloader(client, func(d *manager.Downloader) {
 		d.PartSize = 5 * 1024 * 1024     // 1 MB part size
 		d.Concurrency = 1                 // Concurrent downloads
 	})
 
-	_, err = downloader.Download(context.Background(), ptw, &s3.GetObjectInput{
+	_, err = downloader.Download(context.Background(), progressWriter, &s3.GetObjectInput{
 		Bucket: aws.String(bucketName),
 		Key:    aws.String(oid),
 	})
@@ -199,12 +185,12 @@ func store(oid string, size int64, action *api.Action, writer, errWriter *bufio.
 		// u.LeavePartsOnError = true        // Keep uploaded parts on error
 	})
 
-	progressReader := &progressTrackingReader{
-		Reader:    file,
-		Oid:       oid,
-		TotalSize: size,
-		Writer:    writer,
-		ErrWriter: errWriter,
+	progressReader := &progressTracker{
+		Reader:     file,
+		Oid:        oid,
+		TotalSize:  size,
+		RespWriter: writer,
+		ErrWriter:  errWriter,
 	}
 
 	_, err = uploader.Upload(context.Background(), &s3.PutObjectInput{